Absent most of the year from his official post as chief executive of Apple – he took open-ended medical leave in January – Steve Jobs nevertheless casts a long shadow. He has popped up twice to front product launches, once in March to announce the second-generation iPad, and again in June to unveil the iCloud system, which aims to make PCs and owning music a thing of the past. And last week he announced record second quarter profits of $7.3bn, up 124%, year on year. (He also appeared the following day to persuade his local council in Cupertino, California, to approve a giant new building for Apple.)

For publishers, the iPad has become the consumption device of choice and the trendy way to showcase content. From being an object of some derision – just an enlarged iPhone? – it has cemented its importance for Apple by has sold more than 28m since launch (along with 82m iPhones), and persuaded content creators of all sorts, including Rupert Murdoch, that it is a viable platform for their output.

Apple's App Store delivery method has become a bone of contention for magazine and newspaper publishers unhappy at Apple's skimming off 30% of any purchase price, but despite attempts from rivals offering Google's Android software to challenge its position, the company has the market almost to itself.

Having topped the MediaGuardian 100 last year Jobs is beaten to the top of this year's list by Mark Zuckerberg, in part because he has done nothing in the past 12 months to match the impact of the launch of the original iPhone or iPad, and in part because questions inevitably remain over his medical condition. Nobody is quite sure where the combination of visionary zeal and relentless drive will come from if Jobs's absence becomes prolonged.

Despite a lukewarm reception in 2007, the iPhone is now going strong. With a new version, or even two, expected in September, Apple has overtaken Nokia, once the dominant maker of smartphones, in that sector.

The key is in its apps. Though these existed long before Apple joined the mobile market, it was the iPhone which made them mainstream and hundreds of thousands have been created since 2008. Every content producer now seems keen to build one.

The iPad's iBooks store was expected to be an excellent shopfront for ebooks, but sales have been slower than publishers expected, with Amazon's Kindle instead winning more acceptance – and attention – from readers. Even the Kindle app on the iPad seemed to offer a better choice and use than iBooks.

Apple, however, still looks unstoppable. It was on the brink of disaster when Jobs returned to it after a 12-year absence in 1997. In between he bought a graphics hardware developer that he turned into Pixar and sold to Disney for $7.4bn in 2006. He also founded NeXT Computer, which Apple bought in 1996 for its technology – and to get Jobs back. It turned out to be money well spent.